A technique is known for picking up work pieces using a robot, including a process of capturing an image of randomly accumulated work pieces with a camera, a process of comparing the obtained two-dimensional image with a master model, and a process of holding a work piece if the degree of the coincidence satisfies the predetermined value (See Patent Document 1). As the stored master model, there exists a first master model that includes an entire work piece and a second master model that corresponds to a holding position.